Within present day data processing and signal identification technologies there are many requirements for the classification of an unknown input signal. Typically, such an unknown input signal may be represented in various forms of energy including sound, electromagnetic, visible light, etc. In many prior art systems it was customary to convert such an unknown input signal from its original form of energy to a commensurate electrical signal to render it compatible with electronic data processing and computation techniques and equipments. The capabilities of such electronic equipment in both digital and analog form were thus rendered available to perform the task of classifying an unknown incoming signal, such as, for example, by electronic comparison with a stored library of known reference signals and signal combinations.
Unfortunately, however, electronic data processing computation techniques suffer from the disadvantage that they are basically one-dimensional in nature in the sense that an electron flow has but a single dimension; therefore, the comparisons between an unknown input signal and a stored library of known reference signals and signal combinations must be accomplished sequentially.
Despite the high speed of modern data processing and data computation such a process which is inherently limited to a "one-dimensional" sequential operation can take a considerable length of time to accomplish, with the result that the process may not truly be a "real time" procedure. That is to say, that the comparison process is not completed before another unknown input signal has arrived for identification by subsequent comparison. Of course, those skilled in the pertinent arts will be fully aware that an electronic data processing system can be arranged to operate in a plurality of parallel equipments, but such multiple expansion is costly, adds undesirable complexity, and involves an almost prohibitive number of component elements where a large plurality of parallel equipments are required.
Also known in the prior art are optical techniques for performing correlation processes to identify unknown incoming signals but many of such optical techniques depend upon a special coherent source of light such as a laser which adds to the complexity and maintenance of stringent operational performance as well as contributing undesirably to the overall size of the equipment. Additionally, many of the equipments employed to carry out such optical techniques for performing correlation processes involve moving parts in the form of elements such as oscillating reflective surfaces or revolving mirrors, for example, for performing optical sweeping functions. Such moving elements undesirably add to the problem of synchronism of operation of the equipments in which they are employed and also inherently involve the possibility of a lessened reliability due to unavoidable factors affecting moving parts such as wear, lubrication, vibration, shock damage, etc.
Accordingly, there is a need for a "real-time" multi-channel optical correlation system that will classify an unknown incoming signal rapidly with a high degree of reliability and which can be performed by equipment that is relatively simple, compact in size, has a minimum of stringent maintenance requirements, is devoid of any mechanically moving parts, and additionally can readily accommodate a large plurality of stored reference signals for simultaneous processing.